21178139 has 8 divisors (see below), whose sum is σ = 21565440. Its totient is φ = 20794536.

The previous prime is 21178133. The next prime is 21178151. The reversal of 21178139 is 93187112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21178139 - 2⁴ = 21178123 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21178133) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12272 + ... + 13890.

It is an arithmetic number, because the mean of its divisors is an integer number (2695680).

Almost surely, 2^21178139 is an apocalyptic number.

21178139 is a deficient number, since it is larger than the sum of its proper divisors (387301).

21178139 is a wasteful number, since it uses less digits than its factorization.

21178139 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1849.

The product of its digits is 3024, while the sum is 32.

The square root of 21178139 is about 4601.9712080803. The cubic root of 21178139 is about 276.6703363975.

The spelling of 21178139 in words is "twenty-one million, one hundred seventy-eight thousand, one hundred thirty-nine".